The present invention relates to a fuel delivery system. It finds particular application in conjunction with modern jet aircraft turbine engines, finding particular application during a control system failure, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other applications.
Known fuel delivery systems have proven effective to date to provide desired fuel flow in a wide array of circumstances. Modern jet aircraft engines are now required to prevent even rare occurrences of uncontrolled engine over-thrust during control system failures. Cases of gross over-thrusting engines have resulted in several instances of loss of aircraft control due to substantial asymmetric thrust. As such, the Federal Aviation Administration (FAA) is considering new airworthiness regulations that dictate control system design that will prevent engine over-thrust conditions.
Engine over-thrust conditions are generally caused by a major loss of control functions that result in full fuel pump flow being delivered to an engine combustor. Many schemes are being considered that will bypass the pump delivered flow away from the engine combustor as to control flow delivered to the combustor, and thus engine thrust. These systems require additional hardware features that are independent of the normal control means.
In addition, as jet aircraft engines become more fuel efficient, modern engines have an ever increasingly difficult task of managing fuel system heat. Reduced windmill speeds add to the heat management task by forcing the engine fuel pump to be of a larger capacity, and therefore generate a larger quantity of heat to be dissipated.
Accordingly, there is a need for an improved fuel delivery system which provides over-thrust protection with improved fuel system thermal benefit.